The disclosure relates to an aggregometer for measuring and recording platelet aggregation with at least one measurement cuvette having two electrodes, with a device for moving the liquid to be examined and with measurement and evaluation electronics connected to the electrodes via contact elements.
A known aggregometer of this type (DE 698 21 364 T2) is used to measure and record platelet aggregation. In its protein-rich fluid (the plasma), blood has three main groups of cells, specifically: red blood cells, white blood cells and platelets. Platelets can be exposed to an aggregation-adhesion reaction if they come into contact with particular materials and chemicals. In this case, they change their shape and become approximately spherical. In the process, they develop long appendages and as a result of this they become adhesive. The platelets then adhere to one another and to damaged tissue.
This aggregation is very important, for example, in the case of operations. Aggregation can be reduced by certain medications, but it is necessary to know whether a certain medication dose actually reduces the aggregation, since different people react differently to the medication.
In a known method, the aggregation reaction in samples of platelet-rich plasma is analysed by measuring the transparency of the sample. However, to this end it is necessary to separate the blood in a complex manner by centrifugation, as a result of which the properties of the platelets can be falsified.
In the mentioned prior art, this disadvantage is avoided by mixing the blood which covers two electrodes. If platelets are deposited on the electrodes, the electrical resistance measured will increase and so the aggregation can be determined in this manner. In contrast to other methods, the measurement can also be conducted using blood; centrifugation is not necessary.
Disadvantages of this known aggregometer are, firstly, that the electrodes are ductile and so the electrical characteristics are not constant in the measurement. The stirring rod used to move the blood will locally move the blood vigorously in its vicinity, whereas regions which are situated further away from the stirring rod will be moved less. Both do not correspond to physiological processes in human or animal bodies.
Hence, an aggregometer is provided in which the measurement can be carried out in blood that moves more evenly, without the electrical properties of the electrodes varying.